Good but one big flaw - A-Zoom Rimfire Action Proving Dummy Rounds

The training rounds are as described. They fit 22lr revolvers and chamber properly in semi-auto. The only downside is the hole in the base. I am an instructor. One of the topics in my class is rimfire vs. center fire. Rimfire is difficult to describe because the hole in the base, to a beginner, looks like a place to insert a primer.